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Melting Statues

06/06/2018 10:48 AM

What mechanism causes the often-rubbed parts of bronze statues to wear down? Do the oils in human fingers cause a chemical reaction that leads to breakdown? It is purely friction?

Last weekend someone mentioned the right-foot toes of the statue of St. Peter in St. Peter's Basilica have "melted" off through the centuries from rubbing and pilgrims' tears. That got me thinking about how the process works.

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#1

Re: Melting Statues

06/06/2018 10:52 AM

That's a lot of foot fondling....

...in better days...

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#2

Re: Melting Statues

06/06/2018 11:02 AM

actually wear...

I believe I.M. Pei with one of his designs, he had design a wall with a sharp edge on the corner that people walk next to sliding the hand following the corner, and its literally wore off. I looked but could not find it.

or look at this bank's marble floor

Also you can look at old coinage, some cause by wear as well as tough

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#5
In reply to #2

Re: Melting Statues

06/06/2018 11:45 AM

Or the stone stairs in Thayer Hall at the U.S. Military Academy at West Point. I should have taken some pictures with a straight edge when I was teaching there twenty-something years ago. Of course, this is largely a friction phenomena.

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#3

Re: Melting Statues

06/06/2018 11:11 AM

Copper is not very hard....

..."Brass is an alloy of copper and zinc. Bronze is a metal alloy consisting primarily of copper, usually with tin as the main additive, but sometimes with other elements such as phosphorus, manganese, aluminum, or silicon. Higher malleability than zinc or copper."...

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#4
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Re: Melting Statues

06/06/2018 11:26 AM

I wonder if its not so much the hardness, but the abrasion resistance the material has.

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#7
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Re: Melting Statues

06/06/2018 12:50 PM

Maybe the feet should be waxed regularly...

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#8
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Re: Melting Statues

06/06/2018 12:57 PM

or start putting shoes (not so much the size 37's) on those barefooted statues...

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#9
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Re: Melting Statues

06/06/2018 1:08 PM

Funny you should mention wax.

Most bronze sculptures ARE cleaned and waxed on a regular schedule.

Generally, after a close visual inspection, a spritz with a power washer to remove surface dust/dirt, followed by removal of any surface "stuff" (crayons or graffiti) with mineral spirits. Then a coat of Johnson's Paste wax is brushed on. Yes, there's a specific way to apply the wax. Then, depending on the degree of sheen desired the wax is either left to melt (with heat in colder climates) or applied and buffed.

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#6

Re: Melting Statues

06/06/2018 12:39 PM

It's all part of the patina of the piece. More than likely the result of friction.

I took care of the 30+ pieces of public art on public display in downtown Mesa, Az. for 16 years. Some were painted, some powder coated and one bare steel piece was left to rust naturally.

Since this art is publicly displayed, children are prone to climb onto those close enough to the ground for them to get on. This results in many shiny spots where the original patina has been worn away.

Most bronze sculptures surfaces are treated chemically with the artists favorite witches brew of chemicals to give them their "original" patina but after that they continue to attain their patina after years of exposure to their environment.

Left untouched, they will generally darken in color.

Most sculptures are never repatinated. That would remove the character obtained with age, and might insult the artist. (It is generally accepted that any work or refinishing done to a piece be coordinated with the creator of that piece, if possible)

So, in a word, it's mostly just friction that gives these pieces their patina.

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#10
In reply to #6

Re: Melting Statues

06/06/2018 1:16 PM

GA from me. Thanks! The particular St. Peter statue under consideration is so old I don't know that its sculptor would've treated it with anything, especially since it's sheltered from weather.

What an interesting job! Empire State Plaza here in Albany has a large collection of public art. ("Art historians have called the Empire State Plaza Art Collection "the greatest collection of modern American art in any single public site that is not a museum.") One Alexander Calder painted-steel stabile is being painstakingly disassembled and carted off for restoration. A fountain is possibly not the best place for a piece of metal.

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#12
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Re: Melting Statues

06/06/2018 3:17 PM

Agreed. I met with Lyle London at this site to witness the damage (not patina IMHO) when we were trying to acquire this piece that he had done for the former owners of the building during building demo. Some owners have no real appreciation of art.
Equipoise XII
by Lyle London
This sculpture rises from the tiled fountain area 14 feet high into the six story building atrium.
(Due to legal ownership questions, we were unable to secure it)

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#11

Re: Melting Statues

06/06/2018 3:17 PM

Friction from touching/rubbing is probably greatly enhanced (especially for metal sculptures) by the acids, chlorides and other skin excretions and contaminants on the hands touching the piece.

Acids and chlorides as well as any fine hard grit break the protective corrosion layer and allow the base metal to be attacked. Note that copper alloys will often turn skin black or green when in contact for extended periods.

This means repeated touching of metals statues could be likened to mechanochemical machining. Material is going to be removed at a much greater rate than simple friction alone from such action would suggest.

There may be other factors as well that accelerate removal of frequently hand rubbed metal. Rings, bracelets, or other jewlery on the hands may come in contact with the metal. Minute amounts of jewlery metal or oxidation products could be left and create conditions that increase wear.

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#13

Re: Melting Statues

06/07/2018 7:20 AM

As a kid I was taken to the Vatican on Easter day. We went through the church and a long line of people were passing the statue of saint peter. Each one of them kissed the foot as they went passed. My brother wanted to but my father, an MD, said no, too many possible diseases. I have always wondered what that saliva and other acids would have had on the statue (cant remember if it was bronze or marble). As an aside, we stayed for the popes blessing of the crowd in the square and as he raised his hand I fell into a fountain. So I guess I was baptized by the pope, not that I believe in any form of mumbo jumbo.

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#14
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Re: Melting Statues

06/07/2018 7:38 AM

as a Lutheran, the congregation for communion drank from the same chalais, and about 25 years ago, it was switch to individual disposable plastic shot glasses.

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#15
In reply to #14

Re: Melting Statues

06/07/2018 8:41 AM

Sometimes we (Presbyterians) use intinction to avoid the microbe problem. Maybe if you use real wine the alcohol takes care of it? We eschew alcohol during church services.

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#16
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Re: Melting Statues

06/07/2018 9:00 AM

interesting,... but... digressing farther...

Maybe if you use real wine the alcohol takes care of it?

I'm not sure what you mean by that. And how they went for more sanitary 'dispensing' of the communal wine, was more or less, not only the sanitary as well as etiquette.

Our congregation was not large, but there were a few mishaps that can happen,...

Prior for me getting confirmed,... and I watched communion and the older congregation suffering from ling ailments coughing (farmers that used to be part of the threshing crew in their youth) and the like going up to communion. as a 8 year, I thought that was disgusting as they were coughing right in the chalice...

or...

the Younger ones coughing not expecting the wines strength, the communal wine was very potent ... or even floaters in the chalice to name a few.

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#17

Re: Melting Statues

06/07/2018 10:08 AM

My wife, who is Asian, always wants to rub the belley of the, " Lucky Buddah " . I never quite understood this until I looked at it from another perspective. Over time, from all of the rubbing, the buddah's paunch will be reduced and that must certainly be a good thing.

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#18
In reply to #17

Re: Melting Statues

06/07/2018 10:37 AM

Not working too well for him though

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#19

Re: Melting Statues

06/07/2018 10:53 AM

Here are some photos of statues, and the patina they have acquired over the years.

Big Charlie Black is at ground level and a a big climbing attraction for kids. Most of the oils deposited are removed by the clothing these climbers wear. The original patina is evident on the legs.

Bearly Fishing shows no wear on the mother because she is inaccessible to children.Tokyo Giants. This is granite and was at the entrance of the Tokyo Giants Stadium, in Japan for many years until we acquired it. During subsequent meetings with the family I learned that the dark discoloration was the result of most attendees touching it with their fingers on entering the stadium. In other words, not dirt, patina. It was left unaltered.

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#20
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Re: Melting Statues

06/07/2018 11:34 AM

The pig and the little bear are adorable. Interesting point that the kids' clothing helps protect the statues from oils and so on. How long have these two been on display? And how did you manage to get the Tokyo statue? Was it no longer wanted at the stadium?

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#21
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Re: Melting Statues

06/07/2018 12:22 PM

The pig and bears are about 10 years old. All the pieces were purchased before the last downturn when funding evaporated.

The Tom Ikeda moved from Tokyo and settled in Mesa (where he met and married Janet) and farmed land in what is now downtown. He was an avid baseball fan and after selling their farms he had that statue shipped over to America and placed in their back yard.

They later donated $1 million dollars, and the statue toward construction of the Mesa Arts Center. The arts center, and the city of Mesa, decided that the statue "didn't fit in with their planned theme" for the arts center and it languished in storage, after being removed from their back yard. (By a huge crane parked in front of their house, I was there, and nervous as it was lifted high over their house and swung onto a truck)

About four years ago we moved it downtown and placed in in front of our offices, a block from the arts center. The Ikedas were very gracious and grateful to have it placed in public view, even though they were surely offended by the slight.

There is no mention of the statue in this article.

Family donates $1M to Mesa arts campaign | News | eastvalleytribune ...

Finally, a personal aside, my avatar, The Big Pink Chair, was purchased by my wife and me from a private collection and donated to the children's Mesa I.D.E.A. museum in downtown just before I retired, as a gift for children to enjoy. Because children are encouraged to climb and sit for pictures, it is periodically repatinated. (In this case, re-painted)

Far more than anybody wanted to know, I'm sure.

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#22

Re: Melting Statues

06/09/2018 2:20 AM

I believe it would be a combination of factors. Corrosion products (Patina) protect copper based alloys such as bronze or brass from further corrosion (copper oxides/sulphates etc.).

I would guess that the this protective layer would be destroyed either mechanically (friction) or chemically (chlorides/tears etc) by people touching/rubbing them which would lead to further corrosion and the reforming of the protective layer. An ongoing process leading to "melting".

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#23

Re: Melting Statues

06/12/2018 2:22 PM

Having treated a fair amount of outdoor metal sculpture, airborn dust is probably the number one factor. Human hands are tough and abrasive, often have embedded soils, and will wear through the toughest materials. Dust on a surface, rubbed around by hands, is like sandpaper. That's why they sell white gloves.

The PH of human skin does vary, I had a friend who caused every iron thing he touched to rust. It sucked for him, he was a machinist! The PH of rain is fairly low, it is acidic, so bronze outdoors, or most metal corrodes, I think that is a bigger factor.

Often outdoor bronzes get treated with an acrylic coating with benzoltriazole (a corroson inhibitor) to protect the patina. Unfortunatly, when it fails, it pops off in little flakes and the exposed metal often corrodes at an accelerated rate causing a pit.

This is John Harvard's shoe, worn from many years of being rubbed by tourists and urinated on by students!